Correctly baby's internal sleep clock

After 4 months my baby sucked at sleeping, typical right? Well I accidently slept in and realized he's going to bed at 2am but waking up at 10am. Well I woke him up at 10 so probably longer. Tested my theory and He did this three days in a row. So he knows how to sleep just doesn't know what time it is. We have a routine in place to get him in bed at around 8pm. Have been for 3 weeks now. But he wakes up after a couple hours and won't sleep till after midnight-2am. Any other suggestions?

Thanks,

Very tired & very caffeinated